Seed Dormancy CDNA Library Construct And Selection And Gene Expression Profiling Analysis In Rice (Oryza Sativa L.)

Seed dormancy is a state in which seeds do not germinate even under favorable environmental conditions. Seed dormancy is especially important for cereal crops because it is associated with pre-harvest sprouting (PHS) which frequently happens in China and Southeast Asia and causes great loss of yield and reduction of grain quality. Heavy PHS may occur to more than 5% of the rice in the field, and in some year may be up to 20-30% for hybrid rice. Seed dormancy is a complex trait controlled by polygenes and modified by the genetic background and environmental factors during late stage of ripening.There are many reports on the genetics of rice seed dormancy. To our knowledge, over fifty QTLs for seed dormancy were mapped to rice chromosomes.Despite of this, the molecular basis of seed dormancy was poorly understood. To identify the genes involved in seed dormancy, the researches are as followed:1. Seed dormancy cDNA library was constructed with the seed of N22 from 25 to 35 days after heading. The quality of the library was well with recombine rate of 89% and average length of 1000bp.The cDNA library contained the gene information of seed in the late stage of development.2. Abscisic Acid (ABA) play an important role in seed dormancy.With yeast-one-hybrid system, six clones were identified that can bind to ABRE element through selecting cDNA library.3. A weak seed dormancy mutant line Q4646 was derived by gamma-ray irradiation from the strong seed dormancy indica cultivar N22. The germination rate of Q4646 was more than 40%. Affymetrix GeneChip(?) Rice Genome Arrays were applied on these two lines using RNAs from seed of late stage of maturation and studied their global gene expression pattern differences. The results showed 544 genes were significantly different expressed. These genes were mainly involved in stress response, C-compound metabolism, plant development, DNA processing and lipid metabolism. Expecially, genes encoded heat shock proteins (HSPs), bZIP transcript factor, GA 20-oxidase 1, Cytokinin, Auxin, xyloglucan endotransglucosylase/hydrolase (XTH), Expansin(EXP), Alpha-amylase were significantly changed.These genes may play important roles in seed dormancy. Meanwhile, several differentially expressed genes can be mapped to previously reported seed dormancy QTL loci, suggesting that they may be candidates genes for seed dormancy. Our results provide useful clues for identified seed dormancy gene in future research.4.OsBRE1A and OsBRE1B were cloned that homologous to AtHUBl and AtHUB2. And RNA interference (RNAi) vectors were constructed and transgenic works were took to analysised their functions.